http://api.zip-codes.com/ZipCodesAPI.svc/1.0/<endpoint>?key=<APIKEY>

For XML response data, simply append the URL with XML like this:

You must pass along your API Key for every request.

Use GET or POST verbs.

All query string parameters must be properly URL-encoded.

Use the domain name, not the IP Address as the IP address can shift.

Spaces in a query string parameters may be encoded as + for readability.

This documentation assumes that you have some experience with web requests, specifically RESTful services. It's not only important to know how to make a request, but how to handle the response data that is returned.

Error Information

The API has several errors that mean different things. Below are errors you should know.

Invalid API Key

The API Key that was provided is invalid and reports that Access is denied.

Example JSON Response

{
"Error": "Access is denied."
}

Example XML Response

Endpoint: Get Credit Info

This endpoint will show you how many API requests you have used today, how many API requests used this billing period, how many API requests remain, and when your next billing date is. The API Service has different levels with a maximum number of calls in a given month depending on your service level. This endpoint allows you to accurately gauge how many calls you have been making. Calls to this endpoint do not count against your monthly limit and may be called at any time.

Endpoint: Quick ZIP Code Details

The quick ZIP Details API endpoint provides brief information about the ZIP Code. It is designed to be super fast and provide only the required information for most form autofills. It accepts a single ZIP Code and returns that ZIP Codes city, state, county, and latitude/longitude.